Hacker News Reader

Comment by avz | Hacker News Reader

While water is not uncommon in space, liquid water is a very rare. This is due to the fact that liquids in general can only exist in a relatively narrow range of temperatures and pressures (see phase diagram [1]).

Europa is one of the few places in the Solar system where we expect to find liquid water. One of the others is Mars, but most water there is solid - only small amounts of it occur in liquid form and only briefly. By contrast, Europa has a freaking underground ocean! Moreover, by some estimates it is larger in volume than all oceans on Earth combined [2].

Should we go check it out? Hell yeah!

[1] https://en.wikipedia.org/wiki/Phase_diagram [2] http://apod.nasa.gov/apod/ap120524.html

View on HN

There's more than a dozen solar system objects predicted to have liquid water:

http://www.planetary.org/blogs/emily-lakdawalla/2015/0312171...

Is there any reason why liquid water would not be possible below the surface of planets? Planets with active cores should radiate heat.

Yeah, I understand Mars doesn't have a molten core (anymore), but isn't the center still a lot warmer than the surface?

If so, there is a depth range where water is liquid.

There might be aquifers below the surface of rocky bodies, provided sufficient heat and pressure exist to keep the water liquid. But this would be water in cracks on the rock, or in between grains of sand if sedimentary rocks exist. However, Europa is thought to have actual liquid oceans; these are underneath the ice that is the outer surface of the planet.

It is unlikely for there to be a water layer under rock because it would be gravitationally unstable to have a low-density layer under a higher one.

Imagine selling bottled Europan water. Fiji, move over. That would help fund the mission, and no more battles with environmentalists over Nestle taking too much out of the aquifer etc. of course, that's assuming the Europans won't object.

At a probable price point around 20 million bucks a liter, I'm not sure that there'd be many customers.

I wonder what a water acquisition mission would cost. Under $10 billion? That would require 500 customers at $20 mil each. That's 500 out of several million people who could afford it. Or even more if people pool their resources and spring for a teaspoon of water each. It almost seems like it could be feasible.

That's only 498kg. Considering the Falcon Heavy's payload to Mars is 13,000kg (not sure what the return payload is), that would truly be a reasonable amount of water to bring back. And speaking of Fiji water, they could bring it back in Fiji bottles. Since those bottles have a special ability to make people pay $5 for $.001 of tap water, imagine what they could do with Europan water.

Joking aside, something like this actually could be used to fund space missions. I suspect that some people with hundreds of millions would be willing to pay top dollar for something as exclusive as an item from Europa.

Actually there are people who are looking exactly for items like that to buy. For them the price is more important than anything else. It wouldn't be many, that's true, but it would cover the costs and make a profit.

XKCD has a What If on this very topic:

https://what-if.xkcd.com/143/

Until someone turns on a geiger counter. Europa isn't somewhere you'd like to stand for very long. Jupiter isn't a health spa.

Reply on news.ycombinator.com